Process for obtaining nickel concentrates from nickel oxide ores

ABSTRACT

The nickel grade of nickel oxide ore is improved by the present process of roasting the ore at a temperature above 750*C. whereby the ore is transformed into a forsterite or enstatite structure, pulverizing the calcined ore, mixing the pulverized ore with a reducing agent and a chloridizing agent, pelletizing the mixture and then heating the pellets to effect a segregation reaction. The thus treated ore is concentrated in the usual manner to a high grade nickel concentrate.

United States Patent [191 Ogawa et a1.

[451 Dec. 24, 1974 1 PROCESS FOR OBTAINING NICKEL CONCENTRATES FROM NICKEL OXIDE ORES [63] Continuation-in-part of Ser. No. 23,078, March 26,

1970, abandoned.

[30] Foreign Application Priority Data Mar. 28, 1969 Japan 44-23077 [52] US. Cl. 75/3, 75/119 [51] Int. Cl ..'C22g 1/08, C22g 1/14 [58] Field of Search 75/119, 3

[56] References Cited UNITED STATES PATENTS 3,169,054 2/1965 Weiner 75/3 3,232,743 2/1966 3,318,689 5/1967 3,333,951 8/1967 3,453,101 7/1969 Takahashi et al 75/119 X Primary Examiner-A. E. Curtis Attorney, Agent, or Firm-Robert 1E. Burns; Emmanuel J. Lobato; Bruce L. Adams [5 7] ABSTRACT The nickel grade of nickel oxide ore is improved by the present process of roasting the ore at a temperature above 750C. whereby the ore is transformed into a forsterite or enstatite structure, pulverizing the calcined ore, mixing the pulverized ore with a reducing agent and a chloridizing agent, pelletizing the mixture and then heating the pellets to effect a segregation reaction. The thus treated ore is concentrated in the usual manner to a high grade nickel concentrate.

14 Claims, N0 Drawings PROCESS FOR OBTAINING NICKEL CONCENTRATES FROM NICKEL OXIDE ORES This application is a continuation-in-part of our copending U.S. application Ser. No. 23,078, filed Mar. 26, 1970 and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a process for concentrating nickel ores, especially low grade nickel ores. The present invention is particularly concerned with concentrating nickel ores by a process involving a segregation reaction whereby the nickel content of the ore is gathered in the form of ferronickel particles.

Nickel oxide ores containing silicic acid and magnesia (hereinafter referred to simply as nickel oxide ores), mined in Southeast Asia, Cuba, Czechoslovakia and other countries, are important sources of nickel. Such ores are 'refined by a wet or a dry process, depending on the composition of the ore and the conditions of a particular refinery. The wet process involves High Pressure Sulfuric Acid Selective Leaching, the method whichis applied to a nickel oxide ore bearing little alkali or alkali earth content and Ammonia Leaching, which requires ore blending so that the iron content of the material may be kept constant and at a suitable value, and therefore the variety of ores which are handled by this method is rather limited. On the other hand, the dry process is usually applied where the ore to be treated is serpentine or talc-type garnierite both of which have a relatively low iron content. While the overall output of these ores has steadily increased year after year, the nickel content of the ores appears to be rapidly dwindling.

For example, the nickel content of the oxide ore mined in New Caledonia during the years 1951 to 1960 was 3.3 percent on the average. The average value during the period 1961-1965 decreased to 3.0 percent (estimated) and indications are that the value will drop further to an average of 2.6 to 2.7 percent during the period 1967-1970. If the tendency toward the lower grade persists, the cost of refining nickel ores will increase in the'near future to a level which makes the process unprofitable. Therefore, to cope with the lower proportion of nickel in nickel ores, an effective process for increasing the nickel content of the ores through a metallurgical treatment is needed. The present invention is intended to provide such a process.

Usually nickel oxide ores consist essentially of goethite, talc or serpentine-garnierite and quartz, which invariably contain water of crystallization. Although dependent to some extent upon the place of origin, nickel oxide ore loses the water of crystallization of goethite at 310 to 330C. and that of serpentine and talc-type garnierites at about 650C. and is transformed upon further heating into forsterite or enstatite. The transformation point is usually within the range of 740 to 850C, though it varies according to the location of the mine from which the ore is obtained.

Segregation, which is a widely known process for collecting metallic copper from copper oxide ores and which involves the reaction of a chloridizing agent and a reducing agent with an ore, at elevated temperature is not directly applicable to the concentration of nickel ores because of the various difficulties it involves. For example, nickel ores require more time for the segregation reaction than copper ores, thus raising problems of equipment corrosion. Nickel ores also need higher processing temperatures than do copper ores because of the difficulty in forming nickel chloride due to the characteristic difference between nickel oxide and copper oxide in their behaviors in the chlorination reaction. Further, difficulty is involved in selective extraction of nickel from ores having a large content of iron which tends to show much the same'characteristics as nickel in this kind of chemical reaction. These and other difficulties have rendered it next to impossible to develop a new technique for the concentration of nickel ores.

While some recent work on the concentration of nickel ores by means of the segregation reaction has been reported, segregation processes developed so far require the use of segregation furnace heated by indi' rect means to obtain satisfactory results. As is well known in the art, indirect heating of a furnace involves the use of heating means external to the furnace to pro duce the desired internal temperature, while direct heating involves the use of a heating gas such as a combustion gas which is caused to flow directly into the furnace to provide the desired temperature therein. To effect a reaction at the high temperature necessary for a segregation reaction, i.e. at least about 900C, on an industrial scale indirect heating is uneconomical with respect to the heat efficiency. Also, the difficulties and cost of building a large scale apparatus useful for carrying out a segregation reaction by indirect heating is almost prohibitive due to the high temperature required and corrosive conditions of the reaction.

SUMMARY OF THE INVENTION A principle object of the present invention is the provision of a process for increasing the nickel content of nickel ores.

Another object of the present invention is the provision of a process for concentrating nickel oxide ores to obtain nickel concentrates to be used as materials for fire refining whereby the foregoing difficulties are overcome.

A further object of the present invention is the provision of a process whereby low-grade nickel oxide ores which have heretofore been neglected for economic reasons may be used effectively in an industrial process as a new source of metallic nickel.

According to the invention, the nickel content of nickel oxide ores particularly low grade ores is increased by means of segregation.

It has been discovered that nickel concentrate is obtained in good yield from nickel ores, including low grade nickel ores, by calcining the ore at a temperature of 750C. or above in order to change the mineral composition and transform the ore into the forsterite or enstatite form, then mixing the pulverized ore with a carbonaceous reducing agent and a chloride, pelletizing the mixture and heating the thus-produced pellets to effect a segregation reaction.

DESCRIPTION OF THE INVENTION According to the invention, the ore is dehydrated and calcined to a forsterite or enstatite structure, pulverized, and with the addition of a reducing agent and a chloridizing agent such as sodium chloride or calcium chloride, the pulverized ore is pelletized and dried, and finally the pelletized ore is subjected to roasting to effect the segregation reaction.

The nickel content of forsterite and enstatite seems to be resistant to reduction directly to metallic nickel; when segregation is carried out in accordance with the invention, in the presence of the chloride, reducing agent and the reducing gas produced during the segregation reaction, the nickel content appears to be converted into nickel chloride, by means of chlorine or HCl from the chloridizing agent, and is then reduced by means of hydrogen to nickel which deposits on a carbonaceous substance such as coke. In other words, it appears likely that, in the present process, the reduction of the nickel content of the ore to nickel by way of nickel chloride takes place preferentially, rather than the direct reduction to metallic nickel. The roasting must therefore be accomplished at a temperature of about 750 to 840C. or upwards to convert the ore to the desired form. In view of the nickel grade and yield of the concentrate after segregation, a desirable temperature for calcining ranges from 950 to l050C. The calcining time need not be long, usually a calcining period of about 30 to 60 minutes at about l000C. is sufficient.

It has been found that premixing a reducing agent in the ore has no adverse effect upon the segregation provided that the ore is pelletized after calcining. This is presumably ascribable to the fact that, as already explained, the nickel content of the ore upon calcining is .incorporated in a mineral composition which is not readily reducible directly, and therefore the chloridizing reaction with chlorine or hydrogen chloride which is generated from the chloridizing agent occurs first and then the segregation reaction takes place.

Each pellet containing the reducing and the chloridizing agents constitutes a substantially complete segregation reaction system by itself. Moreover, the larger a pellet, the smaller the relative surface area of the pellet, so that the reaction system is more completely confined in a single pellet. Thus, a common industrial furnace such as rotary kiln which has not been employable previously for this purpose can be used for the present segregation process. The present invention has been carried out satisfactorily, for example, with an internalheating rotary kiln, i.e. a kiln wherein heating is effected partially or completely by means of a heating gas passed through the kiln, commonly referred to as direct heating." When using a rotary kiln it is desirable that the temperature be increased as quickly as possible in the early stage of heating in order to minimize the evaporation loss of the chloridizing agent added. Also, decomposition of the reducing agent in the furnace is accelerated at about 650C., which is an economic problem with respect to waste of the reducing agent. Thus, the quicker the rate of temperature increase of the materials involved in the segregation reaction, the better. The pellets may be fed directly into the reaction zone of the furnace which has been heated to 1000C., for example, in the practice of the present process.

For these reasons, in the process of the present invention where a rotary kiln is to be used specifically as the reaction furnace, a cocurrent type rotary kiln or a counter-current type shortbarrel rotary kiln is preferred.

ln carrying out the present process by direct heating, it is particularly economical to use a combustion gas. The undesirable effects on the segregation reaction of the H and CO in the combustion gas used for heating can be minimized by increasing the pellet size of the charge or thickening the ore layer in the kiln. By combining dehydration, calcining and pelletizing in the manner described, the segregation reaction can be accomplished advantageously using direct heating, as just described.

The pellets of the present invention are generally at least 10 mm. in diameter or larger; generally the pellets used in the present process are about 10 to 30 mm. in diameter but the pellets may be 50 mm. or larger if desired.

By carrying out the process in accordance with the present invention wherein the ore is pelletized after the steps of dehydration, calcination or pulverization, and then after a solid reducing agent and a chloridizing agent have been added to the ore, the segregation reaction may be carried out in an ordinary industrial furnace such as rotary kiln so that the operation is economical and profitable. After the reaction, the product is cooled in such a manner as to avoid oxidation, and nickel is recovered by magnetic or flotation separation. In this way concentrates having a nickel content of 10 to 30 percent are obtained from low-grade nickel oxide ores at yields of about percent or more.

As a reducing agent for the segregation reaction, a carbonaceous solid reducing agent such as coke or anthracite is used. The reducing agent is used in an amount of l to 10 percent based on the weight of the ore. Usually a proportion of reducing agent which is too low results in an insufficient yield of nickel although the grade of the concentrate is high, and conversely too much reducing agent leads to excessive reduction of the iron content and a decline of the nickel content in the resulting concentrate. Thus, the amount of the reducing agent preferably ranges from 4 to 7 percent for coke or from 2 to 6 percent for anthracite.

With regard to the grain size of the reducing agent, it is advantageously in the range of +200 to 60 mesh. If the grains are excessively coarse, the reducing agent does not react adequately and fails to participate in the segregation reaction satisfactorily, with a consequent drop in the nickel grade and yield. If the grains are too fine, the reduction reaction of the reducing agent is intensified and causes the direct reduction of the iron content, again leading to the degradation of the concentrate. For these reasons, the grain size of the reducing agent, for example in the case of coal coke, is preferred to be in the range of +200 to l00 mesh, though it varies to a certain extent with the reducing power of the particular agent.

Calcium chloride is the preferred chloridizing agent, particularly from an economic standpoint. However, other chloridizing agents such as iron chloride may be used. The chloridizing agent is generally used in an amount of about 3jl2% by weight based on the calcined ore, more preferably 7-10% by weight. The grain size of the chloridizing agent is of no importance in the present process; the chloridizing agent may be used in any solid form available or as a solution.

For a successful segregation reaction, a temperature of at least 900C. is required. At temperatures between 800 and 850C. or below, the reaction seldom takes place and practically no condensed nickel concentrate can be obtained by means of subsequent flotation or magnetic separation. At or about 1200C., cohesion among the ore grains increases to such an extent that the flow of the material in the reaction zone is hampered. In view of these facts, :1 segregation reaction temperature between 900 and l200C. is preferred.

The present invention is illustrated in further detail by specific examples which set forth the best mode cur- The composition of the gaseous mixture was 77% N 14% CO and 9% H O, all by volume. After the reaction, the product was cooled in a nitrogen stream and removed from the kiln. It was ground on a vibratory rently contemplated for carrying out the present pro- 5 mill and magnetically separated on a Davis magnetic cess, but which must not be construed as limiting the separator. The results are shown in Table l. invention or scope thereof in any manner.

Table l Pellet Coke Chloridizing Segregation Cone. Ni. Cone. Ni. Example Calcining dia. Agent Temp. Grade Yield N0. Conditions mm. wt7(* 'C. 7r

1 850C. 30 10 cucl, 1000 18.9 74.8

30 min. 10 2 lOOC. 10 10 CaCI 1000 25.2 77.8

30 min. 10 3 1 1000C. 30 10 CaCl, 1000 19.2 83.5

30 min. 10 4 1000c. 30 10 CaCl, 1000 24.0 81.9

30, min. 7 5 lOO0C. 10 CaCI 1150 14.0 90.2

min. l0 6 1000c. 10 10 CaCl 1150 14.9 88.2

30 min. 7 7 1000c. 10 10 NaCl 1000 14.2 81.3

30 min. l0 8 1000C. 10 7 NaCl 1150 12.5 77.2

30 min. 7

based on calcined ore EXAMPLES l-8 In these examples, the ore, composed of 2.85% Ni 30 Co, 12.36% Fe, 23.29% MgO and 42.80% SiO from New Caledonia, was calcined, pulverized, mixed with a chloridizing agent and a reducing agent (coke) having a particle size in the range of +200 mesh to --100 mesh, pelletized to pellets not smaller than 10 mm. in

EXAMPLES 1R-4R Table 2 Pellet Coke chloridizing Segregation Conc. Ni Cone. Ni Example Calcining dia. Wt%* Agent Temp. Grade yield No. Conditions mm. wt%* 7: '7:

1R 700C. l0 l0 CaCl, 1000 9.6 64.4

30 min. 10 2R 700C. l0 l0 CaCl 1000 7.6 56.7

30 min. 10 SR None l0 l0 CaCl l000 9.5 65.3

10 4R None [0 l0 CaCl, 1000 6.7 36.5

based on calcined ore diameter, dried at a temperature not higher than 300C. and subjected to a segregation reaction in a rotary kiln.

More specifically, the ore was calcined to a forsterite structure and was then pulverized. Sodium chloride or calcium chloride was added as the chloridizing agent and pulverized coke as the reducing agent.

The mixture was formed on a pelletizer to pellets either 10 mm. or 30 mm. in diameter. After drying the pellets were charged in a small externally heated rotarykiln of the batch type having a diameter of 80 mm. and a length of 300 mm. With a gaseous mixture of a composition close to a combustion gas being blown through the kiln, the charge was subjected to a segregation reaction at a temperature of over 1000C. for 2 hours.

The following examples (9-12) and comparative examples (SR-8R) show the difference in the results of .eral structure into forsterite or enstatite, or wherein the ore has not been subjected to calcining prior to the segregation reaction.

EXAMPLES 9-10 Lafleur ores A & B having the composition shown in Table 3 were mixed in a 1:1 ratio.

Table 3 N1 Co Fe SiO MgO CaO A1 Cu Cr lg.

Loss

Lafleur A 1.57 0.04 14.56 44.92 15.60 0.54 0.52 0.03 0.27 20.30 Laflcur ples 9-12 were subjected to pelletization, segregation l0 reaction and then worked up using the identical procedures of Examples 9 and 11 respectively, except that the calcination step was omitted. The results are set forth in Table 4.

Table 4 Segregation Reaction by: Direct Heating Indirect Heating Calcination Ni Ni Ni Ni Temperature Conc. Conc. Conc. Conc.

Ex. Grade Yield Furnace Ex. Grade Yield Furnace No. Type No. Type 1000C. 9 14.1 50.6 (a) ll 7.8 91.2 (a) 10 11.6 65.5 (b) 12 9.1 90.3 (b) 700C. 5R 8.0 40.9 (a) 6R 8.6 86.5 (a) None 7R 8.9 36.4 (a) 8R 8.7 87.2 (a) into pellets 10 mm. in diameter by means ofa pelletizer EXAMPLE 13 2 m. -in diameter. Segregation was carried out in a laboratory furnace SUS 27 of mm. diameter heated externally with electricity but provided with means for introducing a gaseous mixture into the segregation reaction mixture either through the top of the furnace (type a) or through the bottom of the furnace (type b). In order to simulate the conditions prevailing during a direct heating process, a gaseous mixture similar to that produced during heavy oil combustion (N 77%, C0 13%, H O 10%) was blown through the top (furnace type a) or bottom (furnace type b) at a rate of 1 liter/min, while the apparatus was heated electrically from the outside. The segregation reaction was carried out at a temperature of 1000C. for 60 minutes.

After the completion of the segregation reaction, the product was cooled, removed from the furnace, ground and magnetically separated on a Davis magnetic separator. The results ofthe foregoing operations are set forth in Table 4.

EXAMPLES 11 AND 12 The same ores in the same proportion as used for Examples 9 and 10 were subjected to calcining and segregatlon and separation under conditions identical with those of Examples 9 and 10 except that during the segregation reaction, the furnace was made airtight and no gas was blown into the furnace during the segregation reaction. The results of these examples wherein segregation is carried out under direct heating are set forth in Table 4.

EXAMPLES 5R AND 6R The same ores in the same proportion used for Examples 9-12 were subjected to calcining at a temperature of 700C. and then the pelletization, segregation reaction and work up were carried out under conditions identical with those of Examples 9 and l 1 respectively. The results are set forth in Table 4.

EXAMPLES 7R AND 8R The sameores in the same proportion used for Exam- An example on a pilot plant scale is shown below.

Ore from Indonesia of a composition of Ni 1.39%, Co 0.08%, Fe 26.47%, SiO 29.20% and MgO 8.49% was calcined at 1000C. for fifteen minutes and pulverized; 4% of anthracite and 9% of CaCl were added to the pulverized ore and the mixture pelletized into pellets of l0-20 mm. in diameter.

The pellets, after drying were continuously fed into a rotary kiln having an inside diameter of 1.2. m. and a 50 Patent is:

l. A'process for obtaining nickel concentrate from nickel oxide ore which comprises calcining a nickel oxide ore at a temperature which is at the minimum at least above 750C, the temperature being sufficient to transform the mineral structure of the ore into that of forsterite or enstatite, pulverizing the calcined ore,

mixing a carbonaceous reducing agent and a chloridizing agent with the pulverized ore, pelletizing the mixture, drying and then subjecting the pellets rapidly to a segregation reaction.

2. A process according to claim 1 wherein the chloridizing agent is sodium chloride.

3. A process according to claim 1 wherein the chloridizing agent is calcium chloride.

4. A process according to claim 3. wherein said segre gation reaction is carried out in an industrial furnace in the presence of a heating gas which is blown into said furnace to provide direct heating of the segregation reactants.

5. A process according to claim 4 wherein the segregation reaction is carried out in a rotary kiln.

6. A process according to claim 1 in which said calcining is carried out at a temperature of about 850 to 1000C., said carbonaceous reducing agent is coke, said chloridizing agent is selected from a member of the group consisting of sodium chloride and calcium chloride and said segregation reaction is carried out in a furnace at a temperature of about 900 to 1200C. in the presence of a heating gas blown through said furnace to provide direct heating of the segregation reactants.

7. A process according to claim 6 in which said reducing agent ismixed in an amount of about 1 to 10% by weight based on the weight of the calcined ore and in which the grain size of said reducing agent is in the range of about +200 to 100 mesh.

8. A process according to claim'6 in which said pellets are about 10 mm. to 30 mm. in diameter.

9. A process according to claim 1 in which the material resulting from the segregation reaction is then concentrated to obtain a nickel concentrate.

10. A process according to claim 4 in which said calcining is carried out at a temperature of about 850 to l000C said carbonaceous reducing agent is coke, said chloridizing agent is selected from a member of the group consisting of sodium chloride and calcium chloride and the segregation reaction is carried out at a temperature of about 1000 to li50C.

11. A process for obtaining nickel concentrate from nickel oxide ore which comprises calcining a nickel oxide ore at a temperature which at the minimum is above at least 750C, the temperature being sufficient to transform the mineral structure into forsterite or enstatite, pulverizing the calcined ore, adding coke dust as a reducing agent and sodium chloride as a chloridizing agent to the pulverized ore, pelletizing the mixture into pellets not less than 10 mm. in diameter, drying and introducing the pellets into a rotary kiln and subjecting said pellets rapidly to a segregation reaction,

and thereafter concentrating the resultant material to obtain a nickel concentrate.

12. A process for obtaining nickel concentrate from nickel oxide ore which comprises calcining a nickel oxide ore at a temperature which at the minimum is at least above 750C, the temperature being sufficient to transform the mineral structure into forsterite or enstatite, pulverizing the calcined ore, adding coke dust as a reducing agent and calcium chloride as a chloridizing agent to the pulverized ore, pelletizing the mixture into pellets of at least 10 mm. in diameter, drying and introducing the pellets into a rotary kiln and subjecting the same rapidly to a segregation reaction, and thereafter concentrating the resultant material to obtain a nickel concentrate.

IS. A process for obtaining nickel concentrate from nickel oxide ore which comprises calcining a nickel oxide ore at a temperature which at the minimum is in the range of about 850 to 1000"C., the temperature being such as to transform the mineral structure into forsterite or enstatite, pulverizing the calcined ore, adding coke dust as a reducing agent and a chloridizing agent selected from the group consisting of sodium chloride and calcium chloride to the pulverized ore, pelletizing the mixture into pellets of not less than 10 mm. in diameter, introducing said pellets into a furnace, blowing a heating gas into said furnace, subjecting said pellets rapidly to a segregation reaction carried out in the presence of said heating gas and thereafter concentrating the resultant material to obtain a nickel concentrate.

14. A process according to claim 1 in which said calcination is carried out at a temperature of about 850 to 1000C., said chloridizing agent is selected from a member of the group consisting of sodium chloride and calcium chloride and the segregation reaction is carried out in an industrial furnace in the presence of a heating gas which is blown into said furnace to provide direct heating of the segregation reactants. 

1. A PROCESS FOR OBTAINING NICKEL CONCENTRATE FROM NICKEL OXIDE ORE WHICH COMPRISES CALCINING A NICKEL OXIDE ORE AT A TEMPERATURE WHICH IS AT LEAST MINIMUM AT LEAST ABOVE 750*C., THE TEMPERATURE BEING SUFFICIENT TO TRANSFORM THE MINERAL STRUCTURE OF THE ORE INTO THAT OF FORSTERITE OR ENSTATE, PULVERIZING THE CALCINED ORE, MIXING A CARBONACEOUS REDUCING AGENT AND A CHLORIDIZING AGENT WITH THE PULVERIZED ORE, PELLETIZING THE MIXTURE, DRYING AND THEN SUBJECTING THE PELLETS RAPIDLY TO A SEGREGATION REACTION.
 2. A process according to claim 1 wherein the chloridizing agent is sodium chloride.
 3. A process according to claim 1 wherein the chloridizing agent is calcium chloride.
 4. A process according to claim 1 wherein said segregation reaction is carried out in an industrial furnace in the presence of a heating gas which is blown into said furnace to provide direct heating of the segregation reactants.
 5. A process according to claim 4 wherein the segregation reaction is carried out in a rotary kiln.
 6. A process according to claim 1 in which said calcining is carried out at a temperature of about 850* to 1000*C., said carbonaceous reducing agent is coke, said chloridizing agent is selected from a member of the group consisting of sodium chloride and calcium chloride and said segregation reaction is carried out in a furnace at a temperature of about 900* to 1200*C. in the presence of a heating gas blown through said furnace to provide direct heating of the segregation reactants.
 7. A process according to claim 6 in which said reducing agent is mixed in an amount of about 1 to 10% by weight based on the weight of the calcined ore and in which the grain size of said reducing agent is in the range of about +200 to -100 mesh.
 8. A process according to claim 6 in which said pellets are about 10 mm. to 30 mm. in diameter.
 9. A process according to claim 1 in which the material resulting from the segregation reaction is then concentrated to obtain a nickel concentrate.
 10. A process according to claim 4 in which said calcining is carried out at a temperature of about 850* to 1000*C said carbonaceous reducing agent is coke, said chloridizing agent is selected from a member of the group consisting of sodium chloride and calcium chloride and the segregation reaction is carried out at a temperature of about 1000* to 1150*C.
 11. A process for obtaining nickel concentrate from nickel oxide ore which comprises calcining a nickel oxide ore at a temperature which at the minimum is above at least 750*C., the temperature being sufficient to transform the mineral structure into forsterite or enstatite, pulverizing the calCined ore, adding coke dust as a reducing agent and sodium chloride as a chloridizing agent to the pulverized ore, pelletizing the mixture into pellets not less than 10 mm. in diameter, drying and introducing the pellets into a rotary kiln and subjecting said pellets rapidly to a segregation reaction, and thereafter concentrating the resultant material to obtain a nickel concentrate.
 12. A process for obtaining nickel concentrate from nickel oxide ore which comprises calcining a nickel oxide ore at a temperature which at the minimum is at least above 750*C., the temperature being sufficient to transform the mineral structure into forsterite or enstatite, pulverizing the calcined ore, adding coke dust as a reducing agent and calcium chloride as a chloridizing agent to the pulverized ore, pelletizing the mixture into pellets of at least 10 mm. in diameter, drying and introducing the pellets into a rotary kiln and subjecting the same rapidly to a segregation reaction, and thereafter concentrating the resultant material to obtain a nickel concentrate.
 13. A process for obtaining nickel concentrate from nickel oxide ore which comprises calcining a nickel oxide ore at a temperature which at the minimum is in the range of about 850* to 1000*C., the temperature being such as to transform the mineral structure into forsterite or enstatite, pulverizing the calcined ore, adding coke dust as a reducing agent and a chloridizing agent selected from the group consisting of sodium chloride and calcium chloride to the pulverized ore, pelletizing the mixture into pellets of not less than 10 mm. in diameter, introducing said pellets into a furnace, blowing a heating gas into said furnace, subjecting said pellets rapidly to a segregation reaction carried out in the presence of said heating gas and thereafter concentrating the resultant material to obtain a nickel concentrate.
 14. A process according to claim 1 in which said calcination is carried out at a temperature of about 850* to 1000*C., said chloridizing agent is selected from a member of the group consisting of sodium chloride and calcium chloride and the segregation reaction is carried out in an industrial furnace in the presence of a heating gas which is blown into said furnace to provide direct heating of the segregation reactants. 